1. Field of the Invention
This invention relates to a process for the preparation of alkenyl dicarboxylic acid lactones by alkenylation of a dicarboxylic acid or its anhydride whereby an alkenyl dicarboxylic acid anhydride is formed together with a sludge and the resultant alkenyl dicarboxylic acid anhydride is subjected to hydrolysislactonization in the presence of said sludge and a catalyst.
2. Discussion of the Prior Art
The preparation of alkenyl dicarboxylic acid lactones is known. Such lactones include alkenyl succinic acid lactone, which is useful as a dispersant in a motor fuel composition or as an intermediate for the preparation of motor fuel and lubricant additives. These alkenyl dicarboxylic acid lactones are particularly useful as gasoline additives to provide a detergent action to an automotive carburetor and to inhibit corrosion in the lines through which the gasoline passes. They are also useful in lubricant compositions or dispersants.
Alkenyl dicarboxylic acid lactones have been heretofore prepared in a multi-step, multi-pot process. In the first step, the dicarboxylic acid reactant, usually in the form of the anhydride, is charged to a reactor into which is introduced the alkenylating agent, typically a low molecular weight polyolefin having a molecular weight in the range of 200-3000. The reaction mixture is stirred while heat is applied to the same. Conventionally, alkenylation is performed at elevated temperatures of up to 300.degree. C. As a result of the alkenylation, the alkenylated anhydride is formed together with a sludge, believed to be a decomposition product of the unsaturated dicarboxylic acid or anhydride reactant.
Lactonization was not effected until the intermediate anhydride was isolated from the unreacted dicarboxylic acid/anhydride and sludge. Generally, this was done by first stripping the unreacted acid/anhydride and thereafter pumping the intermediate sludge mixture over a filter to filter out the sludge and isolate a mixture of the alkenyl dicarboxylic anhydride intermediate in unreacted polyolefin for subsequent lactonization of the anhydride.
The mixture was thereafter charged to still another reactor for lactonization into which was introduced the required agents for hydrolysis-lactonization, usually a minor quantity of water and a catalyst. Lactonization was effected by heating the reaction mixture at an elevated temperature up to 100.degree. C. As catalyst, a protonating or electrophilic catalyst including sulfuric acid, boron trifluoride, perchloric acid and sulfonic acid macroreticular ion exchange resins was used. Lactonization was effected with stirring until the desired product was obtained. The reaction product was thereafter pumped over a second filter to filter out solid material and the liquid was passed into a storage tank. Before use, the liquid lactone produce could be treated with a neutralizing agent such as diethylene triamine to neutralize residual acid values in the product.
It was discovered that notwithstanding the multiple steps required for such alkenyl dicarboxylic acid lactones, that a substantial amount of neutralizing agent was required owing to the presence of substantial quantities of residual acid catalyst in the resultant product. It therefore became desirable to provide a process for the preparation of alkenyl dicarboxylic acid lactones wherein the resultant lactone product could be obtained according to a simplified process. Moreover, it became desirable to provide such a simplified process whereby the resultant lactone product contained substantially less residual acid catalyst.